Illumination based on light emitting diode (LED) has become an effective means for producing the multicolor lighting effects, especially for a dynamic display. Now, the techniques of producing various colors from red light, green light, blue light or more lights with base colors, have been developed.
Nevertheless, there are some problems existing in the application of LED light source, for example, performance of the LED may vary with temperatures and time, as a result, space/color maintenance or human eyes' sensing requirement in some situations could not be achieved. There are some control solutions in the prior art using negative feedback to overcome these problems.
For example, in a negative feedback intensity/color controlled light source, a flux sensor or color sensor is used to detect the output light and the detected result is compared with a pre-calibrated reference. Then an error between the detected result and the pre-calibrated reference is further dealt with the control algorithm and is used to determine the driving current of the LEDs either by means of pulse width modulation or amplitude modulation. In this way, the detected results can be kept to accord with the pre-calibrated reference, and the output illumination intensity or color is accordingly kept steady.
However, there are some problems existing in the prior art. For example, for some solutions, different lighting segments are usually detected in different time periods, which may cause the detected results not real-time. Furthermore, a plurality of sensors may be needed to meet one sensor for one LED array, which may bring side effect on the structure design and cost control of the illumination system. Individual differences among different sensors, as well as differences of the changes of detection performance (e.g. performance attenuation) varying with time among different sensors may lead to differences in the close-loop controlling effects of the illumination system, which is expected to be eliminated in the actual application.